"""



"""

import sys
from sys import stdin

N,K = map(int,stdin.readline().split())

A = list(map(int,stdin.readline().split()))
B = list(map(int,stdin.readline().split()))

C = [ (A[i]-B[i] , i) for i in range(N) ]
C.sort()
C.reverse()

ans = ["B"] * N
for i in range(K):
    nc,ind = C[i]
    ans[ind] = "A"

print ("".join(ans))